At present, although there are far fewer studies on the antibacterial activity of plant extracts against plant pathogens than the insecticidal activity, plants are still considered to be the best development resources for alternatives to chemically synthesized fungicides.

Plant-derived fungicides use certain antibacterial substances contained in some plants or induced plant defense elements to kill or effectively inhibit the growth and development of certain pathogenic bacteria. Antibacterial compounds in plants are a variety of secondary metabolites with antibacterial activity produced by plants, including alkaloids, flavonoids, proteins, organic acids and phenolic compounds and many other types, such as Artemisia serrata Capillin, Saponin. It has been reported that 1,389 kinds of plants may be used as fungicides.

Phytodefensins refer to compounds synthesized by plants and accumulated in plants after they are infected by pathogenic microorganisms, such as Pterocarpans extracted from Erythrina crista Galli L., which are plants The body’s response. The original Pulsatilla extract has a high inhibition rate on the hyphae of Gibberella wheat, which can not only inhibit the hyphae expansion, but also shrink the hyphae on the pathogenic bacteria plate. The 91502-5 preparation is processed from the original Pulsatilla extract. The test results show that the preparation has better control effect and obvious yield increase effect. Coptis contains a large number of alkaloids. In addition to inhibiting the mycelial growth and spore germination of many pathogenic fungi, these alkaloids also have a strong inhibitory effect on bacterial blight of rice.

Plant-derived fungicides are widely present in nature and are an important source for finding ideal fungicides. Four compounds were isolated and identified from the arils of C. sphaerocarpa. Among them, compound II (lα, 2α, 4β, 6β, 8α, 9β, 13-heptahydrocarbyl-dihydro agarwood furan) has bactericidal activity against the pathogen of corn leaf spot The inhibitory virulence of spore germination is 169.29mg/L. The volatile oil extracted from Ephedra and Asarum has a strong inhibitory effect on plant pathogens. The crude extract of Magnolia officinalis leaves has a strong inhibitory effect on a variety of plant pathogenic fungi, and has shown high control effects in potted plants and field experiments.

Plant-derived antiviral agents. Plant viruses are known as "plant cancers". There are currently more than 1,000 species known, whichare very harmful in agriculture, second only to fungal diseases. According to statistics, the world's annual losses due to plant virus diseases exceed 15 billion U.S. dollars. Since most plant viruses have absolute endoparasitic and systemic infectivity, it is difficult to prevent and control plant virus diseases.